When Daisy the Jack Russell terrier went missing from her home in Danville, New Hampshire for almost a month, Karen Forcier, her owner, suspected the worst. According to Danville's Eagle Tribune, Karen had just returned home when Daisy darted out of the open kitchen door. At first, Karen wasn't concerned. Daisy often chased squirrels into the woods. But when her dog didn't return in a few minutes, Karen began to the worry. The following morning, Daisy was still missing, so Karen called Animal Control.

After a month of fruitless searching, Karen had all but given up hope of seeing Daisy again. That is when she received a call from an animal control officer in Bourne, Massachusetts, 106 miles away. Daisy had been spotted walking along the street, looking lost. Workers at the local shelter were able to identify Daisy by the microchip that was imbedded under the skin near her shoulder. This allowed officials to quickly trace Daisy back to her owner. Karen never learned how Daisy ended up so far away, but she was sure the microchip had saved her pet.

Microchips Help Lost Pets Return Home

Millions of lost dogs like Daisy find themselves at animal shelters every year. According to the American Society for the Prevention of Cruelty to Animals (ASPCA), as few as 15 to 20% of lost dogs are ever reunited with their families. Those bearing some form of identification fare much better. Tags and collars work well but can easily break or slip off. Microchips, by contrast, are permanent. The ASPCA states that, when used with a visible tag or collar, a microchip provides the most reliable means of recovering a lost pet.

How Microchips Work

A microchip is a tiny radio-frequency identification (RFID) device about the size of a grain of rice. The device has three parts: a tiny computer chip, some electronic circuitry, and a bio-compatible silicone capsule. It is implanted under the loose skin between a dog's shoulder blades. When it is activated by a specialized handheld scanner, the chip emits an alphanumeric code that uniquely identifies the dog.

As soon as the microchip is implanted, the owner can register the dog's code into a national registry maintained by the chip's manufacturer. This step is critical. If the pet is ever lost and taken to a veterinary hospital or animal shelter where she is scanned, the owner can easily be traced. When all goes well, a missing dog and owner can be reunited in a matter of hours. However, if the owner's information has not been registered with the microchip company or if it has changed and not been updated, there will be no way to identify the dog's owner.

Uses and Benefits of Microchips

Today, microchips are used around the world as an efficient and effective animal identification system. Countries and municipalities are moving toward laws that make electronic identification of companion animals mandatory. This is already the case in Canada, Switzerland, Israel, and Japan. In the United States, microchips have been slower to take hold. Still, they have made possible the recovery of hundreds of thousands of lost or stolen pets since their introduction to the States in the mid-nineties. Humane shelters across the country have begun implanting adoptees with microchips as a matter of course. Fewer unidentified dogs flooding shelters means more room for needy canines awaiting new homes. Microchips are an excellent means of identifying dogs in case of theft. They're also required along with proof of vaccination when importing companion animals to certain countries (for example, if you are moving with your dog to England).

Some Key Benefits of Microchips Include:

They are permanent. Unlike a tag or collar that can slip off or be removed, microchips are designed to last for the dog's lifetime and do not need to be charged or replaced. Reports of device failure or rejection by the animal's immune system are rare.

They are easy and quick to administer. Your veterinarian injects the microchip using a specialized needle and syringe. It only takes a few seconds and is practically painless, causing no more discomfort than a routine vaccine injection.

They cannot be easily removed. Horror stories circulate about dogs being hurt or maimed to remove an identifying tattoo. A microchip is tiny and cannot be felt under the skin, making it nearly impossible for a thief to remove or inactivate the chip.

They are fairly inexpensive. Most veterinarians charge for the chip plus a small fee to administer it. The microchip manufacturer charges an additional one-time fee to enroll the dog in their national database. This cost is usually nominal.

So What's the Catch?

Microchips are a powerful identification tool, but they aren't failsafe. Here are some of the drawbacks:

The microchip may migrate away from its intended location. A small capsule of scar tissue usually develops around the microchip and keeps it in place. But, occasionally, a microchip can come loose from its moorings and migrate to a new spot. This is harmless to the dog, but it can make the device harder or even impossible to detect. It's a good idea to periodically have your veterinarian check that the microchip is in its proper place and in good working order.

The microchip is not a visible form of ID. It will not help a well-meaning neighbor identify your dog when he shows up on their doorstep. The pet must be taken to a veterinarian or an animal shelter that has the proper scanner to decode the hidden message. All microchipped dogs should still wear a visible collar or tag with owner contact information and/or the microchip ID number as a backup.These tags are great for ID purposes.

Microchips have been associated with tumors in laboratory mice. This has been documented in research animals, where microchip technology is widely used. A few anecdotal reports have described tumors adjacent to the implanted device in dogs as well. However, larger studies do not show an increased risk of tumors in microchipped dogs. Most animal care professionals agree that any cancer risk is far less than the chance that a dog will get lost over his or her lifetime.

Infection and bleeding at the injection site are two possible but uncommon complications of microchipping. Be sure to notify your veterinarian if any swelling, tenderness, or discharge develops in the area where the chip was implanted.

Standards and cross-compatibility. Incompatibility issues remain a major pitfall for microchips in the United States. That is, some chips just aren't readable by some scanners. This is true despite the introduction of a so-called "universal scanner" in 2006. Competing microchip companies have resisted the push toward a universal standard, and North American chips and scanners typically fail to comply with accepted protocols worldwide. Today, most animal shelters employ two or more types of scanners to avoid a potentially tragic oversight. And, although microchip manufacturers readily supply readers to animal shelters for free, there are no regulations in place to ensure that they are used. There are still those unfortunate few cases where microchipped dogs have fallen through the cracks.

Stay tuned. As compatibility issues are resolved and new laws are enacted, microchip technology for pets is here to stay. For advice about microchips and your dog, including which, if any, chip format predominates in your area, it's always best to consult your veterinarian.

Disclaimer: This website is not intended to replace professional consultation, diagnosis, or treatment by a licensed veterinarian. If you require any veterinary related advice, contact your veterinarian promptly. Information at DogHealth.com is exclusively of a general reference nature. Do not disregard veterinary advice or delay treatment as a result of accessing information at this site.